linux-kernel - Re: [PATCH RT 3.18] irq_work: Provide a soft-irq based queue

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Date:	Thu, 23 Apr 2015 08:50:26 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	RT <linux-rt-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RT 3.18] irq_work: Provide a soft-irq based queue

On 2015-04-23 08:11, Mike Galbraith wrote:
> @@ -103,6 +98,9 @@ EXPORT_SYMBOL_GPL(irq_work_queue_on);
>  /* Enqueue the irq work @work on the current CPU */
>  bool irq_work_queue(struct irq_work *work)
>  {
> +       bool realtime = IS_ENABLED(CONFIG_PREEMPT_RT_FULL);
> +       bool raise = false;
> +
>         /* Only queue if not already pending */
>         if (!irq_work_claim(work))
>                 return false;
> @@ -110,25 +108,22 @@ bool irq_work_queue(struct irq_work *wor
>         /* Queue the entry and raise the IPI if needed. */
>         preempt_disable();
>  
> -#ifdef CONFIG_PREEMPT_RT_FULL
> -       if (work->flags & IRQ_WORK_HARD_IRQ) {
> +       if (realtime && (work->flags & IRQ_WORK_HARD_IRQ)) {
>                 if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list)))

This boils down to

#ifdef CONFIG_X
some_type x;
#endif
...

if (IS_ENABLED(CONFIG_X) && ...)
	use(x);

And here we even have an indirection for IS_ENABLED via that local bool
variable. Is that pattern OK for Linux? Does it compile in all supported
optimization levels of all supported compilers?

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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